Unveiling the antioxidant and antimicrobial properties of Plumeria pudica Jacq. stem extracts, backed by qualitative and quantitative phytochemical analysis.

Abstract

Background: Since the outbreak of the coronavirus disease, the demand for herbal remedies with minimal or no side effects has risen significantly. This is partly due to the notable side effects, some severe or even fatal, associated with existing vaccines and treatments. As a result, there is growing interest in pharmacological research to address this issue by focusing on organic alternatives to conventional medicines. This approach involves extracting high-quality phytochemicals from plants to develop advanced biomedical applications for treating various diseases and conditions.

Purpose: The objective of this research is to evaluate the qualitative and quantitative phytochemicals present in the stem extracts of the medicinally important plant P. pudica. Additionally, the study includes an assessment of the plant's antioxidant properties and an investigation into its antimicrobial properties.

Methods: The qualitative phytochemical analysis was done to evaluate the presence of various phytochemicals and to quantify these phytochemicals total content estimation of them was done. Also, phytochemical analysis was further enriched by LC-QTOF MS/MS analysis for the presence of compounds. Two assays did the determination of the antioxidant potential of the leaves, the reducing power assay and the DPPH(2,2-diphenyl-1-picrylhydrazyl) assay. With that the antimicrobial properties of the leaves were also put to test against four bacterial strains namely, E. coli, Salmonella enterica, Staphylococcus aureus, and Pseudomonas aeruginosa.

Results: The results of the phytochemical evaluation indicated that both IPA and hydroalcoholic extracts exhibited a superior phytochemical composition, emphasizing the higher extractive potential of HYA compared to the non-polar petroleum ether extract. The quantitative analysis revealed the predominance of HYA and IPA extract as the number of phenols (105.4±0.54 mg GAE/g dry-weight of plant extract), flavonoids (401.2±0.68 mg QE/g dry-weight of plant extract), saponins (233.4±0.45 mg DE/g dry-weight of plant extract) were highest in the HYA extract. Whereas Protein (173±0.7 mg BSAE/g dry weight of plant extract) and alkaloids (167±0.34 mg CE/g of plant extract) were highest in IPA extract.  LC-MS QTOF analysis demonstrated the presence of significant phytocompounds in all stem extracts that have pharmacological applications. Moreover, in antioxidant assays, the HYA extract showed the highest DPPH scavenging activity (70.82 % of inhibition), with an IC₅₀ value of 33.7 µg/mL, and the HYA extract exhibited the highest reducing power (1.57 absorbance), signifying robust antioxidant activity. Furthermore, the antimicrobial evaluation revealed that the IPA and hydroalcoholic extracts displayed activity at lower MIC zones of inhibition compared to the other stem extracts.

Conclusion: This study concludes that the diverse extracts of P. pudica stem possess remarkable phytoconstituent properties both qualitatively and quantitatively, suggesting their rich bioactive compound content and potential as novel sources for therapeutic applications.